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3 years ago

Roy is twice as old as Joan, and in 3 years the sum of their ages will be 21 years. Find their present ages.

Mathematics

1 answer:

Lisa [10]3 years ago

8 0

Answer:

Roy is 10 years old at present and Joan is 5 years old at present

Step-by-step explanation:

Let

x----> Roy's age

y----> Joan's age

we know that

x=2y ----> equation A

(x+3)+(y+3)=21 ----> equation B

substitute equation A in equation B

(2y+3)+(y+3)=21

solve for y

3y+6=21

3y=21-6

3y=15

y=5 years

Find the value of x

x=2y ----> x=2(5)=10 years

therefore

Roy is 10 years old at present

Joan is 5 years old at present

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Which table represents a linear function that has a slope of 5 and a y-intercept of 20?

erastovalidia [21]

Answer:

The first image.

x | y

-4 | 0

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4 | 40

8 | 60

Step-by-step explanation:

To check the slope, we can use the equation (y₂ - y₁) ÷ (x₂ - x₁) using any two pairs given. For this example, I'll use (-4, 0) and (4, 40).

x₂ y₂ x₁ y₁

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~Hope this helps!~

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2 years ago

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kumpel [21]

Answer:

His acceleration is $\frac{1}{15}$ meters per seconds²

Step-by-step explanation:

Acceleration is the rate of change of the speed

The formula of acceleration is $a=\frac{v_{f}-v_{i}}{t}$ , where

$v_{f}$ is the final speed
$v_{i}$ is the initial speed
The unit of the acceleration is meters/second²

∵ Jim goes from 70 meters/minute (beginning speed) to

106 meters/minute (final speed) in 9 seconds

∴ His initial speed $v_{i}$ = 70 meters/minute

- Change it the meter per second

∵ 1 minute = 60 seconds

∴ $\frac{70}{(1)(60)}=\frac{70}{60}=\frac{7}{6}$ meters/second

∴ $v_{i}$ = $\frac{7}{6}$ meters/second

∵ His final speed $v_{f}$ = 106 meters/minute

- Change it the meter per second

∴ $\frac{106}{(1)(60)}=\frac{106}{60}=\frac{53}{30}$ meters/second

∴ $v_{f}$ = $\frac{53}{30}$ meters/second

∵ The time of the change of his speed is 9 seconds

∴ t = 9

∵ The formula of acceleration is $a=\frac{v_{f}-v_{i}}{t}$

- Substitute the values of t, $v_{i}$ and $v_{f}$ in the formula above

∴ $a=\frac{\frac{53}{30}-\frac{7}{6}}{9}=\frac{1}{15}$

∴ His acceleration is $\frac{1}{15}$ meters per seconds²

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Taya2010 [7]

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Answer:

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Step-by-step explanation:

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